Nickel alloys and process of treating the same



iiiti i atcnieoi an '18, 1941 STATES Nielsen ors t; rap

TREATING THE SAME @larence George Biebcr and enter icrcc Bucli, Huntington, WV, ital,

assignora to The International Nichol bcmpany, Inc, New torts, N. ill, a corporation of meiaware duplication .ianuary lit, laid. Serial No. tbdfiibd r em. lci. nal

ihe present-invention relates to improved ace hardenable nicirel alloys and age-hardened articles of manufacture made thereof, and to a process for heat treating such alloys, and more particularly to improved corrosion-resistant age hardenable nichei-copper-aluminurn alloys and improved articles made thereof.

it is well lrnown that corrosion-resistant alloys of niclrel and copper possessed improved properties when aluminum was present in amounts up to li%. i.,ii'i2,'lii to P. D. lvieriea, a nickel-copper alloy was described which contained from l% to jl'i% aluminum and possessed increased hardness and tensile strength while retaining the ability to resist corrosion. it was later found that the physical properties of the alloys could be preatly improved if the alloys were subjected to a heat treatment. Thus, United States'lPatents Nos, 'ijlbbbfi i to 1,755,557 to hiude relate to the method of heat treating nickel-copper-aluminum alloys. The resulting improvement in the properties is attributed to an aee-hardenina etfect. We have now discovered that articles of maniaiacture made of these corrosion resisting niclrelcopper-aluminum alloys possesses further irn proved properties when controlled and critical amounts of titanium are incorporated in the alloy.

it is an object oi the present invention to pro vide age hardened articles'of manufacture made of improved nichel-copper-aluminuni alloys, of the type described in the aforementioned li/ierica and liiiudge patents, containing critical and controlled amounts of titanium and possessina superior hot ductility in the commercial hot worlring range of about ldiid" 15'. to about 23%" hi. without adverse effect on the mechanical properties of the alloys orv the age hardening treatment necessary to produce the same.

it is another'obiect'of the present invention to provide improved age-hardened articles of manufacture made of corrosion-resistant carbonbearina -nickel-copperaluminum-titanium alloys, said aluminum and titanium being present in controlled amounts andsaid articles possessing improved properties.

Titgis a further object of the to provide improved, age-hardened articles of manufacture made of corrosion-resistant carbonbearing nicicel-copper-aluminum alloys which contain controlled and critical amounts of titanium, said articles of manufacture being less susceptible to loss of strength and/or ductility after exposure for long periods of time at elevated temperatures. I The invention "contemplates and wear-resistant articles of manufacture made of certain carbon-bearing nickel-copper- Thus, in United States Patent No;

present invention il.iiii% to about 1% i 2% manganese and about i).(l5% to about 10%* improved corrosion aluminum-titanium alloysand characterized by the ability to retain high properties atelevated temperatures, e. a, at steam temperatures of about lililbi i i The invention further contemplates improved ace hardened carbon-bearing nickelcopperaluminum-titanium alloys characterized by improved hot ductility in the commercial hot workinc range of temperatures and improved physical properties in the ace hardened condition.

it is within the contemplation of the present invention to provide improved age hardenable 'nicirel-copper-aluminum alloys containing critical and controlled amounts of titanium and characterised by improved hot ductility in the hot worrlrina rapes and improved physical properties in the ace hardened condition.

Furthermore, it is also within the contemplation of the present invention to provide an improved process for are hardening the alloys of the present invention and other are hardenable niclrel products, including nickel-copper-aluminum alloys, to impart further improved properties to the alloys, said process involving special and controlled aaine operations.

it is also within the contemplation of the present invention to provide an improved process for ace hardening the alloys of the present in vention and other are hardenable nickel products in which the necessity of a quenching operation prior to aainu is eliminated.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description.

in general, the'invention provides improved age-hardened articles of manufacture made of nicirelecopper aluminum-titanium allows such as those alloys wherein the ratio of nickel to copper is in the neiahhorhood oi two'parts nickel to one part copper.

huitable alloys in accordance with the present invention are those havina compositions within the ranges given in Table i.

present in the alloy withinthe ranges of about silicon, about 0.05% to about iron. p

. We have discovered that articles manufactured from these alloys are particularly im proved when titanium is present in the alloys in iii bit

liable l Element Percentage toss 10-45 i.

at are-1.0 Carbon 0. 05413 in addition, silicon, manganese and iron may be,

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elements in-this process.

' amounts of about 0.4% to about 0.75% and when the aluminum is restricted to amounts ranging from about 2.3% to about 3.4%. The articles can be heat-treated in accordance with the technique developed by Mudge and described in the United States Patents 1,755,554 to 1,755,557, inclusive. Generally speaking, the articles are heat-treated subsequent to mechanical working and forming operations. Under certain conditions the articles may be heat treated before the final operations. For example, fine spring wires may be cold drawn afterthe hardening heat treatment, since this procedure develops the highestphysical properties attainable in the material. a higher luster than can be developed in material which is heat treated after cold drawing. Finish machining may also be carried out after heat treatment to eliminate any discoloration and warping which occur during heat treatment. Heat treated material may be subjected to subsequent machining, stamping, or other fabricating operations whenever necessary.

Hot rolled material having the composition contemplated by the present invention will heat treat to Brinell hardnesses in excess of about 265, and about 300 Brinell represents an average value. Cold drawn or cold worked material in smaller sections, for example up to about one inch in sectional thickness, generally heat treats to Brinell hardness values of about '325 or more. Larger cold worked sections generally do not heat treat to much higher hardness values than hot rolled material of the same sections.

In carrying the present invention into practice, the new articles of manufacture are preferably made of corrosion-resistant nickel-copper alloys having compositions within the more specific ranges given in Table II. Prior to the present invention, the preferred alloys of nickel and copper contained about 3.75% of aluminum and small amounts of carbon, manganese, iron, etc.

While, satisfactory properties can be obtained when the composition is within the ranges given in Table I, it is generally preferred to maintain the composition as near the more specific ranges given in Table II as variations due to commercial production methods will allow. In this manner the best results are assured. Variations from the preferred ranges due to commercial production methods are generally-within the ranges given in Table I.

Table II Element Percentage Nickel 03.0 to 70.0 Copper.. 25.0 to 35.0 Aluminum 2.7 to 3.1 Titanium 0.4 to 0.6

Carbon In commercial practice, silicon, manganese and iron are often present and usually fall within the range of about 0.2% to about 0.4% silicon, about 0.25% to about 0.5% manganese and about 0.2% to about 1% iron.

The aluminum and titanium present in the alloys are considered as major elements in the age-hardening process while the carbon and to some extent the silicon are considered as,minor Iron and manganese apparently affect the base alloy only. When nickel'is said to constitute the balance or when we say that'the balance is substanti l y all" It also produces finished material with nickel, we include within the expression minor constituents and impurities such as cobalt, silicon, manganese, iron, sulfur, phosphorus and other elements commonly present in commercial products. Magnesium is generally not present, as it has been found that magnesium is detrimental to the hot ductility of the materials contemplated by the present invention. We have found that the titanium content is critical and must be at least 0.25% and less than 1% of the alloy. To be of commercial value, the alloys should be capable of heat treatment to a minimum hardness of about 265 to 300 Brinell without cold working and should possess satisfactory hot ductility. Titanium in amounts less than 0.25% produces results which are not appreciably better than that obtained in material containing aluminum only. An alloy containing approximately 2.75% aluminum and 0.50% titanium will readily produce high hardnesses of commercial value. With decreased aluminum contents, the titanium is increased to 0.75% or more. Materials having titanium contents of 1% or more develop a pronounced tendency towards center splitting during rolling into small rods, etc. This center splitting may be considered as a manifestation of poor hot ductility. Consequently, an excess of titanium destroys the beneficial results obtained by a small amount of the element. In addition, no benefits are derived from increasing the titanium contents above 0.75% to 1% while titanium contents of 1% or more are also very ineflicient functionally. Titanium contents above 1.0% require twice as much titanium to produce the same effect as at a level of about 0.5% titanium. The ineffectiveness, or lesser effectiveness, of titanium, when added in amounts in excess of about 0.5% is illustrated in Table III. This table sets forth the hardness of similar materials comprising principally nickel and copper in the ratio of about two to one and containing 2.75% aluminum and various amounts of titanium, as heat treated to maximum hardness without any cold working effect.

Brinell hardness 174 285 302 311 It will be observed from Table III that very little increase in hardness is obtained by increasing the titanium beyond about 0.5% to about 0.75%. The gain in hardness due to the presence of 0.5% titanium is much greater proportionally than the gain due to additional amounts of titanium and, further, the gain in hardness decreases sharply as the total titanium content increases. The high cost of titanium is another serious objection to the use of this element in quantities greater than absolutely necessary. The most economic utilization of titanium is secured when present in quantitles of about 0.4% to about 0.6%. A considerable portion of the physical properties of the materials contemplated by the present invention are due to the presence of carbon. It is therefore preferred to maintain the carbon content at the highest level that is possible without sacrificing hot malleability, since the higher carbon contents impart increased strength and hardness. Whereas carbon is highly detrimental in high titanium alloys of nickel and copper, it is highly beneficial and even necessary in material made in accordance with the present invention.

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Table IV Percent Percent Percent Brinell Ti Al hardness None 3. 63 302 0. 20 3. 03 156 None 0. 53 2. 93 241 0. 20 0. 53 2. 93 302 The behavior of the high titanium material in the presence of carbon is believed to be explained by the formation of an inert titanium carbide which decreases the hardening efiiciency of the titanium. The fact that the presence of carbon increases the physical properties of material made in accordance with the present invention indicates that'inert titanium carbides do not form as in the case of the high titanium material and that carbon is highly beneficial in low titanium material.

The advantageous use of restricted amounts of titanium and aluminum in the alloys does not conflict with the heat treatment technique described in the Mudge patents. Titanium and aluminum in amounts within the contemplation of the present invention offer marked improvements in the age hardening properties of the alloys. The hardness and strength of articles made of the old nlckel-copper aluminum alloys are increased about 10 to l5% or more without appreciable decrease in ductility when made in accordance with, the present invention. The alloys used in the present invention may be heat treated in the same manner as thenickel-copper-aluminum alloys but are preferably treated in accordance with an improvement thereover which will be described more fully hereinafter.

Articles manufactured in accordance with the present invention are also less susceptible to loss of strength and/or ductility after exposure for long periods of time at temperatures of approximately 500 F. to, approximately 1100 F. Such articles retain their high properties at elevated temperatures, for instance, at steam temperatures of about 1000 F. Table V compares the properties of prior titanium-free material with our improved titanium bearing material in the as heat treated condition and after heat treating and aging for months at 000 F.

Table V Material Condition LP. B. S. gaf Forcing;

Titanium-heal Heattrcstcd' 86.5 148.3 25.0 46.3 o Heat aged... 95.0 153.0 17.5 24 4- Titanium-bear- Hcattreatcd 97.8 150.5 28.0 45.4.

ion Hestagcd. 1l3.5 l65.0 24.0 are Y. P.=yield point in thousand pounds per square inch.

' B. S.=brealzing strength in thousand pounds per square inch.

Percent El.=pcrcent elongation in 2 inches. Percent R. A.=pcrcent reduction of area.

. The improved high temperature stability of the titanium-bearing material is particularly notice able in the loss of ductilityin the older titanium free material; C he titanium-bearing material also possesses a higher yield point and breaking strength than the prior material. Under certain conditions the titanium-free material exhibits marked decreases in strength after being subjected to elevated temperatures for long periods v of time.

The titanium-bearing material possesses improved'hot ductility without detrimental efiect upon the mechanical properties or the method of heat treatment necessary to procure the mechanical properties. The alloys of the present invention possess improved hot ductility within the hot working range of about 1400" F. to about 2300" F. The diflferences in hot ductilities between the titanium-free and the titanium-bearing alloys contemplated by the present invention are very pronounced. For example, a titanium-bearing alloy had a hot malleable range of about 000 F. or more; whereas atitaniumfree alloy had a hot malleable range of only about d00 F. Data from typical melts are given in Table VI.

Table l f Material Hot {malleabl range 0 1900 to 2300 1500 to 2300 Titanium-free Titanium-bearing The difference in hot malleability between the titanium-free material and the titanium-bearing material represents the difference between material which is not commercially malleable and material which is commercially malleable. Articles of manufacture made in accordance with our invention are also corrosion-resistant, oxidationresistant, wear-resistant, hard, strong, machinable, non-magnetic, etc.

In accordance with the present invention, improved articles of manufacture, for example, valve parts, pump pistons, turbine blades, etc., are satisfactorily made of the alloy given in Table 0H.

The material is mechanically worked as desired into the required shape and heat treated to ageharden the material. Preferably the heat treatment is conducted in accordance with the improved methods discussed more fully hereinafter, the best heat treatment being dependent upon the finishing temperature of the mechanical treatment and the amount of cold worlr imparted to the material.

Some of the advantages of the present invention are illustrated in Tables VH1 and flit which give the composition and properties of a titaniumfree heat-treated alloy containing 3.00% alumimum and of another made in accordance with a preferred embodiment of the present invention and containing 3.01% aluminum and 0.53% titanium. The improved properties of the titaniumbearing material are readily observed.

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Table VIII Composition in percent Per- Per- Per- Per- Per- Per- Per- Per- Percent cent cent cent cent cent cent cont cent 1 Ni Cu Al Ti, C Si Mn Fe Mg A 66.15 29.90 3.00 None 0.15 0.25 0.25 0.30 None B G5. 75 29.72 3.01 0.53 0.16 0.25 0.23 0.32 None Table IX Physical properties N o Hardening heat treatment R. A. El. 7

Y. P T. S. B. H. perpercent cent Au. 1100 F. for 16 hrs. 82,000 136,000 212 41.0 31.0

followed by slow cooling to 900 F. B do 120,000 107,000 321 37.0 26.0

Y. P.=yicld point in pounds per square inch. '1. S.=tens1le strength in pounds per square inch. B. H.=Brinel1 hardness number. R. A. percent=peroent reduction of area. El. peroent=percent elongation in 2 inches. pb

The improved heat treatment contemplated by the present invention imparts higher mechanical properties to heat treated titanium containing material having compositions within the ranges herein set forth than is obtained by conventional heat treating procedures. Tensile properties are obtained which are higher by about 10,000 to 15,000 pounds per square inch, or even more, than can be obtained by other known methods of heat treatment. Thehigher tensile properties are obtained without substantial de-, crease in ductility.

In general, the heat treatment involves a novel aging procedure which comprises a combination of one or more holding periods at predetermined temperature and one or more controlled and critical slow rates of cooling to lower tem peratures. The alloys of the present invention need not be and preferably are not quenched prior to aging in order to render them susceptible to age hardening, i. e., the use of a high temperature quench is not necessary. The alloys are usually quenched only when it is desired to have the alloys in the soft condition, 1. e., to prevent them from age hardening during cooling following hot working or annealing operations. Alloys of the present invention which are inthe annealed condition have been quenched or rapidly cooled. The alloys will harden to substantially the same final hardness, regardless of whether they have ever been subjected to any quenching or rapid cooling operation during any stage of processing. As a matter ofconvenience, in order to render the material soft and easy to straighten, chip and'overhaul, as well as to prevent danger of cracking during reheating, rods, billets, and blooms are generally quenched after each hot'working operation. The initial temperature of the aging treatment and the amount of time required for the complete treatment is determined by the amount of cold work which the material has received since its last annealing or hot working operation. In practice, the material is preferably held at a temperature of about 1000 F. to about 1225 F. for from about onehalf hour to about 16 hours, or more, and subsequently cooled more or less continuously to a temperature of about 900 F. to about 800 F. at a rate not exceeding about 75 F. per houran'd preferably about 50 F. or 25 F. per hour or even less, e. g. 12 F. per hour. While the rate of cooling down to a temperature of about 1100 F. may be more rapid, e. g., 75 F. per hour, the rate of cooling below about 1100 F. should not exceed about 50 F., and should preferably be about 25 F. or less .per hour. Theoretically the maximum properties appear to be developed by cooling at not more than about 15 F. per hour down to about 900 F. and at about 4 F. per hour from about 900 F. down to about 800 F. The increase in mechanical properties with decreasing temperature is continuous although at a decreasing rate. Thus, material having the compositions contemplated by the present invention which have been cooled slowly to 900 F. in accordance with the improved heat treatment will have higher properties than would have been developed had the slow cooling been terminated at 1000 F. Below about 800 F. the increase in properties is so slow that for practical reasons the slow cooling is seldom continued below this temperature, and often is discontinued at about 900 F. Incommercial applications, the material may be quenched, air cooled or cooled at any convenient rate from the final temperature, e. g., from about 800 F., down to atmospheric temperatures. A quenching operation after the hardening treatment decreases the total time consumed in the heat treatment.

When it was required to increase the physical properties above those obtained by the conventional treatment, it has generally been necessary in the past to cold tap the product to meet the required physical properties. This practice resulted in extra cost and also'in the splitting of a large percentage of finished products during heat treatment. The improved aging process imparts higher physical properties without having to resort to cold tapping. The process has been used effectively in aging not only the nickel-copper-aluminum-titanium alloys but has also been used satisfactorily to age harden other nickel products having compositions rendering them age hardenable. Age hardenable nickel products containing aluminum and titanium, or aluminum, or titanium, or aluminum and another age hardening element which have been treated in the improved manner, without being quenched prior to aging, have developed high hardnesses and other high physical properties.

The initial temperature of the improved aging treatment and the amount of time required is considerably aifected by the cold worked condition of the material being treated. In general, it is preferred to use lower initial temperatures the greater the amount of cold work. The following examples are illustrative of the preferred procedures which will develop near maximum properties in material with and without various amounts of cold work.

EXAMPLE No. I

' 1100 F. at a rate of between about 25 F. and

about 75 F. per hour, preferably about 50 F. per hour, and subsequently cooled at a controlled rate not exceeding 50 F. per hour, preferably about 25 F. or less per hour. to a temperature within the range of about 800 F. to about 900 F,

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EXAMPLE No. II

Material which has received a moderate amount of cold work, such as halt-hard temper strip, cold drawn rod, etc., develops near maximum properties when held within the temperature range of about 1050" r'. to about 100 r'. for about 0 to about 16 hours and subsequently cooled at a controlled rate not exceeding 50 F.

per hour, preferably about 25 F. or less per hour,

EXAMPLE No. ill

Material which has received a large amount of cold worlr, such as spring temper wire and strip, develops near maximum properties when held at a temperature within the range oi about 1000". l to about 1050" F. for from d to 0 hours and subse quently cooled at a controlled rate not exceedillg 50 F. per hour, preferably 25 lb. or less per hour, to a temperature within the range of about 800 15. to about 000,F., e. an,- 000" F.

The improved mechanical properties obtained by our method of age hardening are not due to the increased time required for the amine treatment. The following example demonstrates that the higher properties obtained by our improved heat treatment are not the result at lonuer aging. A one inch diameter hot rolled rod having the composition oi. the alloy 0 elven in Table IQ was treated by our improved method,

i. e., aged at about l080.F.'for about it hours vliollowed by cooling at about 25 F. per hour to about 000 F. Another rod of identical composition was heat treated in the conventional manner for about 00 hours at about l000 l followed by the usual furnace coolinc at a rate or about 200 h". per hour. The tensile properties obtained by these two treatments are given in Table K. Prolonged heat treatment in the con ventional manner does not produce the hinher properties obtained by our improved process.-

l'ublc It Heat treatment P. L. Y. P. B. 8 El. R. a.

Longtime conventional. 64. 0 94. B 153. 3 25. 0 l7. 0 improved process 76.0 100.0 163. 5 23.0 42.5

I. L.=pro ortional limit in thousand pounds per square inch Y. P.===yic d point in thousand pounds per square inch.

B. S.=brcaking strength inthousand pounds per square inch. lEL=elongatlon in 2 inches in percent.

1R. A.= reducti n;.of area in percent.

For the purpose of giving those skilled in the art a better understanding oi the invention, we

set forth herelnbefore.

TcblaXI Element Alloy 0 Alloy 1) Alloy E Alloy r Percent Percent Percent Percent EXAMPLE No. IV

Hot rolled rods, /1 inch diameter, having the composition of Alloy C were annealed at l450 l t. Some or the rods were then heat treated in the conventional manner for about 16 hours at about 1080 F. and furnace cooled at theusu'al rate of approximately 200 F. per hour. Another batch of annealed rods was heat treated in the improved manner for about 1 hour at about i200 bl, cooled at a rate of about50 F. per hour to about ll00 l t, and cooled from about 1100 F.

' to about 000 F. at a rate of about F. per

P. L.=proportionel limit in thousand pounds per square inch. P. o.=proof stress in thousand pounds per square inc fiY. g.=yield point 111 thousand pounds per square inch (0.2 percent B. S.=brealcing strength in thousand pounds per square inch. EL=elongation in 2 inches in percent. R. A.=reduotion of area in percent. 13. H. N.=Brinell llardness number.

. ltuluurrn No. if-

l-lot rolled rods, inch diameter, having the composition oi Alloy C were subjected in the as hot rolled and quenched condition to heat treatment in the conventional and improved manner. Conventionally heat treated rods were held for about 10 hours at about 1080 F. and furnace cooled at approximately 200 per hour. Rods heat treated in the improved manner were held at about 1080 'F. for about 10 hours and then slowly cooled to about 800 F. at a rate oi about 25 0. per hour. Some of the resulting physical. properties are given in Table w.

Table .ltlll See footnote to Table XII for key.

Emitters No. ill

Bold drawn rods, l.l25 inches diameter, having the composition oi Alloy D were heat treated in the as cold drawn condition in accordance with conventional practice and in accordance with the improved procedure. The conventional process comprised heating to about l0B0 F- and holdllle for about l2 hours, then furnace cooling at a rate of approldmately 200 F. per hour. The improved proccdurecomprised heating to about 1000" F. and holding at that temperature for ltd ltd

dlUl

lid

lid

about 12 hours, and then cooling at a rate of about 25 F. per hour to about 800 F. The P y ical properties possessed by the rods are given in Table IHV.

Table XIV Heat treatmen: P. L. P. S. Y. P. B. 8 El. R. A. B. H. N]

As cold drawn 80. 87.0 99.0 116.0 23. 5 47. 8 g 235 Conventional. 103.0 117.0 135.0 164. 7 19.0 34. 5 321 Improved..." 114.0 124.0 142.0 174.0 18.0 32.8 341 Si-c footnote to Table )III for key.

EXAMPLE No. VII

for about 6 hours at about 1050 F. and cooled about 25 F. per hour to about 800 F. Table XV gives some of the physical properties of the strip.

Table XV Heat treatment P. L. P. S Y. P B. S E].

As cold rolled 68.0 81.0 128.0 139. 5 10. 5 Conventional 118.0 133. 3 151.0 174.2 12. 5 Improved 130.0 143. 5 164.0 183. 5 l2. 0

See footnote to Table XII for key.

The present invention contemplates improved age-hardened articles of manufacture characterized by improved hot ductility during processing and possessing increased strength, hardness, etc., without appreciable decrease in ductility. Typical examples of such articles include rollers and bearing balls, bearings and races therefor, roller chains, non-magnetic drop forgings and tie rods for airplane construction, valve seats and other valve parts, pump rods and the like, pump rod sleeves, pump pistons for high pressures and temperatures, p'lungers, turbine blades, turbine diaphragm blading, lock washers, screws and nuts, tools, cutting blades and the like, pins and needles springs and other resilient elements, airplane instrument parts, nozzles for burners, rods. sheets, strip, wire, 'bars, rolled shapes, etc.

Although the present invention has beendescribed in conjunction with preferred embodiments, it is understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand.

We claim:

1. An age hardened wrought article of manufacture made of a nickel-copper alloy comprising 25% to 35% copper, 2.7% to 3.1% aluminum, 0.4% to 0.6% titanium, not more than 1% silicon, 0.13% to 0.2% carbon and ,the balance substantially all nickel, said article having been subjected during processing to mechanical hot working operations and to heat treatment whereby an improved article is produced containing controlled amounts of titanium, aluminum and carbon within the aforesaid ranges while at the same time ssessing high mechanical properties, in-

eluding a hardness of about 300 Brinell, improved resistance to embrittlement when exposed to elevated temperatures for long periods of time and improved freedom from splits and the like compared to an article made of a similar alloy not containing titanium in the aforesaid amounts.

2. An age hardened nickel-copper alloy possessing improved hot malleability comprising 25% to 35% copper, 2.3% to 3.4% aluminum; 0.4% to 0.75% titanium, not more than 1% silicon, 0.13% to 0.2% carbon and the balancesubstantially all nickel, said alloy containing controlled amounts of titanium, aluminum and carbon within the aforesaid ranges being characterized by improved hot ductili J within the hot working range of about 1500' F. to about 2300 F. combined with improved freedom from splits and cracks as compared to a similar alloy not containing titanium in the aforesaid amounts, and said alloy being age hardened to hardnesses in excess of'about 265 Brinell hardness number while at the same time possessing improved resistance to embrittlement when exposed to elevated temperatures for long periods of time.

3. An age hardened nickel-copper alloy comprising 10% to 45% copper, 2% to 4% aluminum, at least 0.25% and less than 1%. titanium, not more than 1% silicon, 0.05% to 0.3% carbon, and the balance substantially all nickel, said alloy containing controlled amounts of titanium, aluminum and carbon within the aforesaid ranges being characterized by hot ductility within the hot working range of about 1500 F. to about 2300 F. and by improved resistance to embrittlement'when exposed to elevated temperatures for long periods of time combined with high hardnesses exceeding about 265 to about 300 Brinell hardness in the aged condition when subjected to an aging process which comprises holding said alloy at temperature within the range of about 1000 F. to about 1225 F. for from about onehalf hour to about 16 hours and. subsequently cooling substantially continuously to a temperature within the range of about 900 F. to about 800 F. at a controlled rate not exceeding about F. per hour through any temperatures above about 1100 F. and at a controlled rate not exceeding about 50 F. per hour through temperatures below about 1100 F. whereby an improved alloy is obtained possessing improved hot malleability and fndom from splits and cracks while at the sametime possessing improved mechanical properties and improved resistance to embrittlement at elevated temperatures.

4. An age hardenable nickel-copper alloy comprising 25% to 35% copper, 2.3% to 3.4% aluminum, 0.25% to 0.75% titanium. not more than 1% silicon, 0.05% to 0.3% carbon, and the balance substantially all nickel, said alloy containing controlled amounts of titanium, aluminum and carbon within the aforesaid ranges being characterized by hot ductility within the hot working range of about 1500 F. to about 2300 F. and improved freedom from splits and cracks after hot working as compared to a similar alloy not containing titanium in the aforesaid amounts 'while' at the same time being age hardenable to which comprise holding saidalloys containing controlled amounts of titanium, aluminum and carbon in the aforesaid ranges at temperature within the range of about 1000 F. to about 1225 F. for from about one-half hour to about 16 hours and subsequently cooling substantially continuously to a temperature within the range of about 900 F. to about 800 F. at a rate not exceeding about 50 F. per hour through any temperatures above about 1100 F. and at a controlled rate not exceeding about 25 F. per hour through temperatures below about 1100 whereby higher hardnesses are imparted to said alloys than byheat treating similar alloys by a process involving furnace cooling said alloys at the conventional slow rate of about '200 F. per hour.

6. In the process of age hardening nickel-copper alloys containing 10% to 45% copper, 2% to 4% aluminum, at. least 0.25%

balance substantially all nickel, the steps which comprise holding said alloys containing controlled amounts of titanium, aluminum and carbon in the aforesaid ranges at temperature within the range of about 1000 F. to about 1225 F. Iorfrom, about one-half hour to about 16 hours and subsequently cooling substantially continuously to a temperature within the range of about and less than 1% titanium, 0.05% to 0.3% carbon, and the 900 F. to about 800 F. at a controlled rate not exceeding about 75 F. per hour through any temperatures above about 1100 F. and at a controlled rate not exceeding about 50 F. per hour through temperatures below about 1100 F. whereby higher hardnesses are imparted to said alloys than by heat treating similar alloys by a process involving furnace cooling said alloys at the conventional slow rate of about 200 F. per hour.

'I. The process of age hardening nickel alloys containing 10% to 45% copper, 2% to 4% aluminum, at least 0.25% and less 0.05% to 0.3% carbon, and the balance substantially all nickel, which comprises heat treating said alloys containing controlled amounts of titanium, aluminum and carbon within the aforethan 1% titanium, 7

said ranges in the substantially unquenched con dition at predetermined aging temperatures and subsequently cooling substantially continuously at a rate not exceeding 50 F. per hour to minimum eifective aging temperatures whereby higher hardnesses are obtained in said alloys than by heat treating similar alloys by a process involving furnace cooling said alloys at the conventional slow rate of about 200 F. per hour.

CLARENCE GEORGE BIEBER. MORTIMER PIERCE BUCK. 

